Greetings to all. I finally got to really test my Permatrims today, on a run between Anacortes (Skyline) and the Port of Edmonds. 2 adults, 3/4 fuel in both tanks, very little gear. My observations: 1. Absolutely improved ability to keep the bow down into the chop. 2. Felt like it was planing at lower speed, with even less perceptible transition between displacement and planing than before 3. Phenomenal fuel economy. I have no data basis for the exact impact of Permatrims, but I got 5+ MPG in a four hour run with an average speed of about 18MPH, mostly with bow down into flat water (Skyline through Skagit bay) and 1-2' chop (Saratoga Passage to Edmonds). This is better than I'd ever gotten before and makes me very happy. 4. With one engine shut off and lifted out of the water, one of my Honda 40's planes the boat with a top speed of 17MPH. I run low pitch props, and the engine could only make 5400 RPM or so, and clearly felt overworked. I wouldn't recommend running this way for more time than is required by an urgent situation. 5. Permatrims absolutely impart lateral trim ability with the twin engines. I don't have trim tabs and now have no need for them. 6. I didn't get as much stern lift as I'd hoped for, and the boat still will not run at the same level attitude as my old 22Cruiser/Johnson70 did. The bow came down, but the stern didn't come up as much as I'd hoped. 7. My Permatrims run appx. 2" below the water's surface at planing speeds, with the Permatrim visible but water clearly running over the top of the plate. According to the MFG. this is not optimal for getting the most out of the Permatrim. I still have 2" of upward adjustment in the motor bracket, and will consult with Les about the possibility of raising the engines. 8. Top speed remained the same as before at 30MPH. I may have squeezed out 31MPH before Permatrims but I think I remember it being 30 back then as well. 9. I did not notice any difference in ease of steering, and don't have enough pre-Permatrim wheel time to comment on Permatrim's effect on low-speed handling. Overall I'm very happy with this product and would recommend them to anyone. I observed no negative handling or performance effects as a result of Permatrim installation. Hope this helps a fellow C-Brat. Mike.
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Permatrim sea trial
- Thread starter westward
- Start date
Thanks for the report. I just installed a permatrim on my boat too, but have not had the opportunity to sea-test it yet. With all the wonderful reports here about it, I may be setting my expectations too high though!!!!
Received excellent service from the dealer in WA when I had a question on installation; he called back immediately with an answer to my question.
Jeff
Received excellent service from the dealer in WA when I had a question on installation; he called back immediately with an answer to my question.
Jeff
Rob & Karen
New member
I would be curious to know where the Permatrims on other boats are in relation to the water while on plane. Mike said his is 2" below the surface. In another thread Bob Austin said his is above the water. I know my anti-cavitation plate is below the surface while running.
Reading the Permatrim web site, it seems like the only way a Permatrim may negatively affect performance is if your engine is mounted too low on the transom. I have been considering installing a Permatrim, but I am concerned about the engine height....don't want to drill ten holes in the engine and then find out it ran better before.
Rob
Reading the Permatrim web site, it seems like the only way a Permatrim may negatively affect performance is if your engine is mounted too low on the transom. I have been considering installing a Permatrim, but I am concerned about the engine height....don't want to drill ten holes in the engine and then find out it ran better before.
Rob
Hi Rob. I saw the bit on the Permatrim website about engine height and it makes me think that I might get an even greater performance boost by raising the engines. But nevertheless they are already a major improvement on my boat. They allowed me to plane at a remarkably low speed, which must have contributed to my fuel economy by eliminating the power surge required to get back on step after I'd slowed down to avoid flotsam, handle a bigger wave, etc. I will report Les Lampman's remarks re: engine height once I get a hold of him. The Permatrim website recommends an engine height that leaves the ventilation plate flush with the hull bottom, and mine are set lower than that. I'm wondering what factors determine engine height, and if raising mine would expose them to cavitation damage, etc. Mike.
From my experience as an outboard mechanic.
The plate on the lower unit where the Permatrim is mounted is called an 'anti-ventilation plate' and its purpose is to prevent air from being sucked down into the spinning prop.
A good starting point is to mount the motor so that the A-V plate is flush with the bottom of the boat. On high speed boats, the motor is raised up to reduce drag. On C-Dorys(not a high speed boat), flush probably will be fine. If the motor repeatedly sucks air into the prop in tight turns(ventilates), or big waves, then lower the motor one hole on the transom bracket.
The higher the motor on the transom, the less drag and the faster the boat can go. (Not usually important on a C-Dory). The lower the motor on the transom, the more resistance to ventilating, but there is more drag, which slows the boat.(Again, not usually important on a C-Dory.
The plate on the lower unit where the Permatrim is mounted is called an 'anti-ventilation plate' and its purpose is to prevent air from being sucked down into the spinning prop.
A good starting point is to mount the motor so that the A-V plate is flush with the bottom of the boat. On high speed boats, the motor is raised up to reduce drag. On C-Dorys(not a high speed boat), flush probably will be fine. If the motor repeatedly sucks air into the prop in tight turns(ventilates), or big waves, then lower the motor one hole on the transom bracket.
The higher the motor on the transom, the less drag and the faster the boat can go. (Not usually important on a C-Dory). The lower the motor on the transom, the more resistance to ventilating, but there is more drag, which slows the boat.(Again, not usually important on a C-Dory.
I agree with Larry on engine height. Any boat with an engine bracket hull extension, the engine is moved about 1 inch up for every foot back from the hull as I recollect, thus the Tom Cat engines are going to be higher than the non bracketed boats.
I will be considering moving the outboard up one hole on my 25 also after I put the permatrim on.
I will be considering moving the outboard up one hole on my 25 also after I put the permatrim on.
Rob & Karen
New member
Bob,
If you decide to move the engine up one hole, will you do it yourself, or have it done by an outboard mechanic?
Rob
If you decide to move the engine up one hole, will you do it yourself, or have it done by an outboard mechanic?
Rob
Bob,
I agree on the 1 inch up for every 1 foot back for bracketed motors.
It is a good idea on raised motors to have water pressure gauges, to monitor the cooling system. Raised motors can draw air into the water pickups and starve the powerhead for cooling water.
Very high speed boats, (60-90mph) use a 'low water pickup' located at the bottom of the gearcase to prevent loss of cooling water. The pickup is located on a 'nose cone' extension that is installed over the nose of the gearcase. This modification most likely would NOT be needed on a Tom Cat.
Larry H
I agree on the 1 inch up for every 1 foot back for bracketed motors.
It is a good idea on raised motors to have water pressure gauges, to monitor the cooling system. Raised motors can draw air into the water pickups and starve the powerhead for cooling water.
Very high speed boats, (60-90mph) use a 'low water pickup' located at the bottom of the gearcase to prevent loss of cooling water. The pickup is located on a 'nose cone' extension that is installed over the nose of the gearcase. This modification most likely would NOT be needed on a Tom Cat.
Larry H
Westward
What a great report on your new Permatrim hydrofoil. That is one of the things I have been looking for. I have some concerns that maybe you can answer for me.
A few months ago I spoke to Andy at SIM. One of my concerns was the bolt heads on top of the cavitation plate inducing drag underway. He said it was not a problem, because when underway the top of the Permatrim is out of the water. If that is the case, why would there not be air coming in under the front of the Permatrim? My question went unanswered.
I am interested in putting a hydrofoil on my motor. I have heard wonderful reports about the Permatrims on this site. I can see how they improve directional stability. As big as they are, I can see how they easily keep the bow down. With the top and the bolt heads out of the water on plane, how do you not have a cavitation problem?
What a great report on your new Permatrim hydrofoil. That is one of the things I have been looking for. I have some concerns that maybe you can answer for me.
A few months ago I spoke to Andy at SIM. One of my concerns was the bolt heads on top of the cavitation plate inducing drag underway. He said it was not a problem, because when underway the top of the Permatrim is out of the water. If that is the case, why would there not be air coming in under the front of the Permatrim? My question went unanswered.
I am interested in putting a hydrofoil on my motor. I have heard wonderful reports about the Permatrims on this site. I can see how they improve directional stability. As big as they are, I can see how they easily keep the bow down. With the top and the bolt heads out of the water on plane, how do you not have a cavitation problem?
Dave wrote:
The Permatrim mounts on top of the anti-ventilation plate. I don't know what kind of boat you have but on the C-Dory monohulls the bottom of the AV plate is to be level with or slightly below (1/16") the plane of the bottom of the hull. Therefore, the Permatrim will not affect the original performance or operation of the motor in that respect, it is simply positioned above. I have twins, they work great, no negative affect on ventilation in hard turns.A few months ago I spoke to Andy at SIM. One of my concerns was the bolt heads on top of the cavitation plate inducing drag underway. He said it was not a problem, because when underway the top of the Permatrim is out of the water. If that is the case, why would there not be air coming in under the front of the Permatrim? My question went unanswered.
I am interested in putting a hydrofoil on my motor. I have heard wonderful reports about the Permatrims on this site. I can see how they improve directional stability. As big as they are, I can see how they easily keep the bow down. With the top and the bolt heads out of the water on plane, how do you not have a cavitation problem?
With the motor fully or mostly trimmed down, my Permatrim has an eyeball attitude of probably 10-15 degrees greater than the flat plane of the hull bottom. I think it acts like a big scoop ramming a solid stream of water through the prop wash. There probably is enough water back pressure up front to keep most of the air out. At any rate, I have noticed no cavitation on mine but I haven't been out with anyone where I have been able to really observe my operational depth. Using a 4 foot long level along the hull bottom while on the trailer, it looks as if the lead edge of my cavitation plate is maybe a half inch below level at trim down. It may be as much as 3" at a more bottom level trim. I am very interested to hear the results of anyone's efforts to lift their engine a notch.
I added 2 - 2" MMM safety strips across the top of my slippery Permatrim so that it is a little safer to use as a transom swim step for the kids while the engine is turned off. Also a second nut to insure no sharp bolt edges. Water's still a bit to cold to see how this works out.
chris
I added 2 - 2" MMM safety strips across the top of my slippery Permatrim so that it is a little safer to use as a transom swim step for the kids while the engine is turned off. Also a second nut to insure no sharp bolt edges. Water's still a bit to cold to see how this works out.
chris
mmitchell,
Sorry your question wasn't answered previously. I've stated in previous threads that I have both Bennett Trim Tabs (TT) and a Permatrim and I definitely feel that the Permatrim is an added benefit. In fact, I prefer using the Permatrim to adjust the bow attitude, it really gets the nose down in the water. At this point, I use the TT's mostly for lateral trim.
We had a Permatrim (PT)on our original motor and really liked it. We tried just going with TT's on the new motor and found that the boat porpoised at higher speeds and even while adjusting for bow down, it didn't seem to adjust the bow as efficiently as the PT. I ended up installing the PT and was instantly reminded why we liked the PT. It felt as though the boat was tracking on rails and it really reduced the porpoising effect.
This is my $.02 and of course YMMV.
Peter
C-Dancer
Sorry your question wasn't answered previously. I've stated in previous threads that I have both Bennett Trim Tabs (TT) and a Permatrim and I definitely feel that the Permatrim is an added benefit. In fact, I prefer using the Permatrim to adjust the bow attitude, it really gets the nose down in the water. At this point, I use the TT's mostly for lateral trim.
We had a Permatrim (PT)on our original motor and really liked it. We tried just going with TT's on the new motor and found that the boat porpoised at higher speeds and even while adjusting for bow down, it didn't seem to adjust the bow as efficiently as the PT. I ended up installing the PT and was instantly reminded why we liked the PT. It felt as though the boat was tracking on rails and it really reduced the porpoising effect.
This is my $.02 and of course YMMV.
Peter
C-Dancer
mmitchell":3h2h5nbf said:Question?
Are the Permatrims really a value added addition to the performance of the boat if the trim tabs are used properly?
mmitchell-
Yes, the Permatrims
1. promote planing earlier, reducing time for the hole shot and therefore speed up initial aceleration,
2. provide more planing area, allowing the hull to carry more weight effectively,
3. effectively lengthen the hull out behind the trnsom, making the boat ride better in chop,
4. channel water with their downward turned outer edges, enhancing steering control,
5. help control ventilation of the prop on tight turns, eliminating some washout and over-reving the engine in the process,
6. provide a platform to stand on and till up and re-enter the boat in a man overboard situation,
7. allow more precise and a greater range of control over bow up/down trim when used in conjunction with trim tabs,
8. provide an enlarged mounting platform for a trolling plate or engine mounted trolling motor when compared to the standard limited size anti-ventilation plate,
9. etc., etc.,
My $0.02, YMMV (your mileage may vary)
Joe. :teeth :thup
I'll add a #10 to Joe's post: Largely eliminate the need for trim tabs in a twin engine application. I've had trim tabs fail on another boat and I like it that the Permatrims are a passive system. They require no holes be drilled in the hull which is a huge plus in my mind. I also suspect that those with single engine/trim tab setups appreciate having their trim tabs freed up in the neutral position, rather than fully down to keep the bow down, to get the best lateral trim. Mike.